<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      function srr(opa) {
        var n1 = +prompt('请输入第一个数字');
        var n2 = +prompt('请输入第二个数字');
        if (opa === '+') {
          alert(n1 + n2);
        } else if (opa === '-') {
          alert(n1 - n2);
        } else if (opa === 'x') {
          alert(n1 * n2);
        } else if (opa === '/') {
          alert(n1 / n2);
        }
      }
      srr('+');
    </script>
  </body>
</html>
